Future research into C 4 Biology
This Special Focus Issue (Vol. 57, Issue 5) of Plant and Cell Physiology is organised and guest edited by Mitsutaka Taniguchi, Andreas Weber and Susanne von Caemmerer and highlights the current trends in C 4 photosynthesis research; both from the viewpoints of understanding its trajectory from C 3 -type photosynthesis and of the biochemical, genetic and physiological processes involved.
Editorial: Future Research into C 4 Biology *FREE*
Mitsutaka Taniguchi, Andreas P.M. Weber, and Susanne von Caemmerer
C 4 photosynthesis occurs in relatively few angiosperms commonly adapted in living in challenging environmental conditions, such as drought, high temperatures, intensive sunlight etc., yet it accounts for a significant proportion of terrestrial photosynthesis. This SFI, comprising 3 reviews and 5 research articles, is dedicated to the latest research and leading ideas on C 4 biology, including its trajectory from C 3 types and C 3 -C 4 intermediates, to the prospect of eventually engineering C 4 -like photosynthesis in C 3 species.
The Road to C 4 Photosynthesis: Evolution of a Complex Trait via Intermediary States
Urte Schlüter and Andreas P.M. Weber
The most efficient mode of terrestrial photosynthesis - C 4 photosynthesis - independently and convergently evolved more than 60 times from the ancestral state of C 3 photosynthesis. This review discusses the evolutionary trajectories that lead from C 3 to C 4 photosynthesis via stages of C 3 -C 4 intermediacy, which enables the evolution of such complex traits in many small steps, rather than in one giant leap. Understanding the mechanisms underlying this gradual evolutionary process might provide a blueprint for synthetic experimental evolution approaches aimed at introducing C 4 photosynthesis into C 3 crops.
Starch Accumulation in the Bundle Sheaths of C 3 Plants: A Possible Pre-Condition for C 4 Photaosynthesis
During the evolution of C 4 photosynthesis, various genetic, biochemical and anatomical pre-conditions of C 3 plants were recruited. These C 3 pre-conditions are now the focus of active investigations to clarify the evolutionary trajectory from C 3 to C 4 . This review discusses the starch-accumulating activity of bundle sheaths in some C 3 plants and in particular how they might contribute towards a pre-condition for C
Promotion of Cyclic Electron Transport around Photosystem I with the Development of C 4 Photosynthesis
Yuri Nakajima Munekage and Yukimi Y. Taniguchi
C 4 photosynthesis has repeatedly evolved from C 3 photosynthesis in various plant families. This review discusses how during such events, the development of the C 4 metabolic cycle greatly increased the ATP demand in chloroplasts for the malic enzyme-type C 4 photosynthesis, and how additional ATPs may in turn have been produced by enhanced cyclic electron transport around photosystem I. Further studies using knock-down transformants with reduced cyclic electron transport around photosystem I will provide a model for energy production in C 4 photosynthesis.
Mesophyll Chloroplast Investment in C 3 , C 4 and C 2 Species of the Genus Flaveria
Matt Stata, Tammy L. Sage, Natalie Hoffmann, Sarah Covshoff, Gane Ka-Shu Wong, and Rowan F. Sage
Mesophyll cells of Flaveria species were examined to determine where along the evolutionary transition from C 3 to C 4 reductions in the number of chloroplasts and coverage of the cell periphery occurs. These two traits declined with increasing strength of C 4 metabolism and alterations in expression of genes needed for assembly of the plastid division contractile ring. These mesophyll plastid features, which are present in 12 other lineages, are posited to be essential for efficient C 4 function by enhancing CO 2 diffusion to cytosolic PEPcase.
Targeted Knockdown of GDCH in Rice Leads to a Photorespiratory Deficient Phenotype Useful as a Building Block for C 4 Rice
Hsiang Chun Lin, Shanta Karki, Robert A. Coe, Shaheen Bagha, Roxana Khoshravesh, C. Paolo Balahadia, Julius Ver Sagun, Ronald Tapia, W. Krystler Israel, Florencia Montecillo, Albert de Luna, Florence R. Danila, Andrea Lazaro, Czarina M. Realubit, Michelle G. Acoba, Tammy L. Sage, Susanne von Caemmerer, Robert T. Furbank, Asaph B. Cousins, Julian M. Hibberd, W. Paul Quick, and Sarah Covshoff
Loss of glycine decarboxylase from mesophyll cells is a key early step in the evolution of C 4 photosynthesis. Here, OsGDCH was targeted for degradation preferentially in rice mesophyll cells using an artificial microRNA. Knockdown plants had a mild photorespiratory phenotype and significantly reduced chloroplast coverage of the mesophyll cell area and peripheral cell wall. The gdch knockdown lines are an important building block for engineering C 4 rice.
Metabolic Network Constrains Gene Regulation of C 4 Photosynthesis: The Case of Maize *FREE*
Semidán Robaina-Estévez and Zoran Nikoloski
The transcriptional signature of the C 4 syndrome has already been extensively described in the maize plant model. Here we integrate the publicly available transcriptomics data sets into large-scale metabolic networks in maize to show that the structure of the metabolic network imposes constraints at the transcript levels. Our findings have implications for future engineering attempts of the C 4 syndrome, which would appear to require extensive fine-tuning of gene expression.
Growth Properties and Biomass Production in the Hybrid C 4 Crop Sorghum Bicolor
Youshi Tazoe, Takashi Sazuka, Miki Yamaguchi, Chieko Saito, Masahiro Ikeuchi, Keiichi Kanno, Soichi Kojima, Ko Hirano, Hideki Kitano, Shigemitsu Kasuga, Tsuyoshi Endo, Hiroo Fukuda, and Amane Makino
Hybrid vigor has been used as a breeding improvement technique to achieve enhanced biomass production, however the physiological mechanisms underlying heterosis remain poorly understood. Here we show that sorghum hybrids often exhibit enlargement of leaf area with lower N content, leading to higher N-use efficiency for CO 2 assimilation, however their photosynthetic properties do not differ from the parental lines. This suggests that the increase in biomass is predominantly due to the extended vegetative phase in hybrids.